This application claims priority of Taiwan patent Application No. 90205625, filed on Apr. 11, 2001
1. Field of the invention
This invention relates to an antenna for an electronic device.
2. Description of the related art
Wireless communication devices, such as cellular phones, notebook computers, electronic appliances, and the like, are normally installed with an antenna that serves as a medium for transmission and reception of electromagnetic signals. The antenna can be built outside or inside the devices. However, the latter (built-in type) are more attractive due to a tendency of folding and breaking for the former upon use.
FIG. 1 illustrates a conventional plate-type antenna 1 which is commonly known as PIFA (Planar Inverted-F Antenna) and which includes a rectangular conductive radiating plate 11, a rectangular conductive grounding plate 12 that is vertically spaced apart from and that is electrically connected to the radiating plate 11 via a conductive grounding leg 13, and a conductive signal feeding leg 14 that projects from one side of the radiating plate 11 and through an opening in the grounding plate 12 (the signal feeding leg 14 is spaced apart from the grounding plate 12) and that is adapted to be electrically connected to an electromagnetic transmitter and an electromagnetic receiver (not shown).
Frequency, input impedance, and bandwidth are key parameters for the design of an antenna for a specific use, and are mainly, but not exclusively, related to the dimension of the radiating plate 11, the dimension of the grounding plate 12, and the position of the electrical contact between the signal feeding leg 14 and the radiating plate 11. The parameters are interrelated such that a modification in one of the parameters causes corresponding changes in the other two.
The aforesaid conventional antenna is disadvantageous in that since the dimension of the radiating plate 11, the dimension of the grounding plate 12, and the position of the electrical contact between the signal feeding leg 14 and the radiating plate 11 are all fixed, it can only be used for a specific application that requires a specific frequency, input impedance, and bandwidth, and thus lacks flexibility.
Therefore, it is an object of the present invention to provide a plate-type antenna that is capable of overcoming the aforementioned drawbacks.
It is another object of the present invention to provide a slot-type antenna that is capable of overcoming the aforementioned drawbacks.
According to one aspect of this invention, there is provided a plate-type antenna for an electronic device. The plate-type antenna comprises: a conductive radiating plate unit; a conductive grounding plate unit vertically spaced apart from and electrically connected to the radiating plate unit; and a conductive signal feeding leg electrically connected to the radiating plate unit, spaced apart from the grounding plate unit, and adapted to be connected to an electromagnetic transmitter and an electromagnetic receiver. At least one of the radiating plate unit and the grounding plate unit is extendable to adjust the behavior of the antenna.
According to another aspect of this invention, there is provided a slot-type antenna for an electronic device. The slot-type antenna comprises: a conductive main plate extending in a longitudinal direction, formed with a slot, and having a first plate portion that surrounds the slot and that defines a periphery of the slot, and a second plate portion that extends from one side of the first plate portion in a transverse direction relative to the longitudinal direction; a conductive signal feeding leg electrically connected to the first plate portion of the main plate and adapted to be connected to an electromagnetic transmitter and an electromagnetic receiver; and a conductive extension plate electrically, adjustably, and selectively connected to one of the first and second plate portions so as to permit extension and retraction of the main plate in the longitudinal direction and vary the dimension of the slot that is exposed from the main plate and the extension plate when the extension plate is connected to the first plate portion, and so as to permit extension and retraction of the main plate in the transverse direction when the extension plate is connected to the second plate portion.